1. Field of the Invention
The present invention generally relates to fermenters utilized in the controlled growth of cells, and more particularly, the present invention relates to a fermenter having the accuracy and range of control of laboratory fermenters and the component accessibility, ruggedness and economy of industrial fermenters.
2. Description of the Prior Art
In the growth of cells or cultures under controlled conditions, it is necessary to have a vessel in which the pressure, temperature and other desired variables may be adjusted as required or desired. Such a pressure vessel must be sterilizable, in order to prevent the intrusion of any undesired cells or organisms. This is frequently done by separate autoclaving, but it is preferable to be able to sterilize in place, especially with large industrial-type fermenting equipment.
In order for the variables to be properly adjusted, it is necessary to have readily accessible control components. Such control components are frequently buried in a complex control panel, making accessibility and replacement difficult. Further, if it is desired to have different control conditions for successive runs of the fermenting equipment, the necessary modifications may involve a major effort.
Another aspect of fermenting equipment is that provision must be made to agitate the nutrient bath in order to obtain the desired dispersion of the cells, as well as to retain introduced gases in solution until they have been absorbed or otherwise utilized by the cells. This means that provision has to be made for driving the impeller blades without interfering with the pressure seal of the pressure vessel or contaminating the contents in any way. A related problem is the mounting of the drive motor on the apparatus. As the mounting structure and the motor are normally located on top of the fermenter, these items present a significant mass on the upper portion of the fermenter with the attendant mechanical and thermal loss problems.
One of the serious defiencies of current industrial-type fermenters is that while they are generally rugged and relatively economical, they involve a very significant weight and size, with the attendant handling problems. In many cases, special large equipment is required for such handling, and the flexibility of the fermenter is very limited. As the mounting of such large devices usually involves heavy heat-conducting-type metals, the thermal conductivity creates difficulties in maintaining desired temperature conditions at the pressure vessel.
Sterilization and temperature control of the pressure vessel is normally achieved by introducing a suitable fluid between the surrounding jacket and the pressure vessel. For sterilization, steam is usually utilized, while tap water would normally be used for cooling purposes. Such an approach leads to tap water contamination, as well as internal scale buildup between the jacket and the vessel, with the resulting loss of temperature control.
As a result of the size and cumbersomeness of conventional industrial fermenters, access to the interior of the pressure vessel is normally quite limited. This creates significant difficulties during the transition from one operating cycle to another, as well as limiting the efficiency of the equipment.